Safety driving connection for drill strings



Aug. 1933.

2. WITKIN SAFETY DRIVING CONNECTION FOR DRILL STRINGS Filed Aug. 28, 1929 gwuemtoc Zara PVz'f/tin duotum Patented Aug. 22, 1933 UNITED STATES,

PATENT OFFICE SAFETY DRIVING CONNECTION FOR DRILL STRINGS This inventionrelates to drilling apparatus for drilling deep wells, such as oil wells, and particularly to the apparatus used in rotary drill and may, in some cases, necessitate the aban- 5; donment of the well, involving extremely expensive delays and great economic waste.

The general object of this invention is to provide means for avoiding such difiiculties and to provide safety means which will prevent the drill string from being subjected to a destructive torque.

A further object .of the invention is to pro-' vide means located just below the kelly, at which point repairs can be made in case the torsion being impartedto the drill string would, without this device, rupture the string. v

A further object of the invention is to provide simple means for facilitating the replacement of the frangible connections which are intended to shear if the torque rises to a dangerous degree; also to provide means "operating to insure centering of the driven member with the driving member and thereby insure that the frangible means will be subjected only to shearing forces. This insures an accuracy in the point at which the shearing of the frangible means occurs.

One of the objects of the invention is to provide a construction of this kind which will still support the drill string after the frangible means 40 have been sheared.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and Figure 2 is a vertical section through my safety connection and showing the lower end of the kelly, and also illustrating the connection at the lower end of the device to the drill string, which is broken away.

Figure 3 is a horizontal cross-section taken about on the line 3-3 of Figure 2.

Figure 4 is a side elevation of a frangible pin and showing details of its preferred form.

In practicing the invention I provide an upper driving member which is supported for rotation by the rotary table and this member presents an annular supporting shoulder. I also provide a lower driven member provided with means for connecting the sameto the drill string. These 0 two parts are connected by a connecting member which is preferably attached to the driven member, and this connecting member is formed with an annular flange which projects laterally from it and is supported on the annular shoulder. With this combination I employ frangible means through which the driving movement is imparted from the upper member to the driven member. The frangible means has a cross-sectional area sufficient to insure that it will shear before the torsional stress, that is, the torque to which the drill string is subjected, would twist off the drill string at any point.

The connection between the connecting member and the driven member is preferably a thread connection. In order to prevent the development of too great friction between the driving mem-' ber and the connecting member at their contact faces after the frangible means has been sheared, I prefer to form one of these faces with a webbed surface, as will appear hereinafter.

Obviously, these general features of construction may be embodied in various specific constructions. I shall now proceed to describe one embodiment of such constructions.

Referring'to Figure 1, 1 represents the cellar or pit which is formed in the ground 2 at the location of the hole. Above this cellar the derrick floor 3 is located which supports a rotary table 4 of the usual construction. Through this rotary table the kelly 5 passes downwardly. According to my invention, between the kelly 5 and the upper end of the drill string 6 I provide a connection 7 embodying my improvements. So far as I know, I am the first to provide any kind of a safety connection at this point directly below the kelly.

The safety connection '7 preferably comprises a tubular housing 8 which is of reduced diameter above and threaded for connection to the threaded lower end of the kelly. The lower end of the housing 8 is preferably of relatively larger diameter and carries a relatively heavy transverse head 9 at its lower end, which has a central opening 10 so that an annular supporting shoulder or face 11 is formed around the opening. This tubular housing constitutes an upper driving member for the connection whichis, of course, rotated by the kelly when it is rotated by the table.

I provide a lower driven member 12 which is formed at its lower end with threads for connecting it to a coupling 13 which is in turn connected to the upper end of the drill string 6. The driven member 12 is supported on the annular shoulder 11 through the agency of a tubular connecting member 14 which is provided at its upper end with a laterally extending head 15 the under face of which rests on the face of the shoulder 11.

In order to center the driving member 8 on the driven member 12, I prefer to provide the upper end of the driven member 12 with an enlarged head 16 which has a conical upper face 17 that is received in a similar conical counter-bore or end face 18 formed at the lower end of the head 9. The lower end of the connecting member 14 has'a thread connection 19 with the driven member 12.

In'order to impart the driving movement and also to provide means for limiting the amount of torque that can be imparted to the drill string 6, I provide frangible means through which the driving movement is imparted. This frangible means may be of any suitable form and located in any desired manner for imparting the movement from the driving member 8 to the driven member 12. However, I prefer to provide for this purpose a plurality of frangible pins 20 which are received in a plurality of aligning sockets 21 and 22 formed respectively through the flange 15 and in the upper side of the shoulder 11.

These pins 20 have a definite area, and by employing a material of known shearing strength, I am enabled to provide a total area for these pins which will shear at approximately '75 percent of the torque which would twist off the drill string at its weakest point. This gives a sufficient margin of safety for practical purposes.

In order to facilitate the removal of sheared pins, I provide an opening 23 through the flange 15 which is located on the same radius as the centers of the pins 20 and by bringing these openings into alignment with the sheared off pin, the pin can be pulled up through the opening. In order to facilitate this, I prefer to provide each pin with a short neck 20 of reduced diameter at which the shear will take place. This neck should be located substantially in line with the upper face of the shoulder 11. With this connection it vwill be evident that if the torque being imparted rises to a dangerous point, the pins will shear off and permit free rotation of the housing 8; that is to say, it will permit independent rotation of the housing with respect to the drill string.

It will be evident that when such a shearing of the pins takes place, a considerable torque might be imparted frictionally between the flange 15 and the shoulder 11.. In order to reduce the amount of this friction and, consequently, the transmissible forces, I form one of these meeting faces with a ribbed surface as indicated by the line 24 (see Figure 2). These ribs are preferably in the form of circumferential ridges with circumferential grooves or recesses between them. This reduces the area of contact,

What I claim is: 'f

1. In safety drilling apparatus to be connected to the upper end of a drill string in drilling a deep well with a rotary table, the combination of a tubular housing driven at its upper end, said housing having a head at its lower end with a central opening through the same with an annular supporting shoulder formed on the upper face of the head, a driven member disposed below the housing and having means for connecting the same to the drill string, a tubular connecting member extending down through said central opening and attached to the driven member, and having an enlarged head at its upper end forming an annular projecting flange seating on said annular shoulder to support the drill string, and frangible cylindrical driving pins passing down through the upper face of said flange and into the said annular shoulder, imparting the rotary movement to the driven member, said pins operating to shear and permit free rotation of the housing when a predetermined torque is being imparted through the same.

2. In safety drilling apparatus to be connected into a drill string in drilling a deep well with a rotary table the combination of a tubular housing having means for connecting the same to a driving member, said housing having a head at its lower end with a central opening through the same with an annular supporting shoulder formed on the upper face of .the head, and projecting inwardly from the wall of the casing, the under side of said head having a substantially conical face with the elements of the conical face inclining downwardly toward the periphery of the housing, a driven member disposed below the housing and having a substantially conical upper face substantially abutting against the first-named conical face, a tubular connecting member extending down through the said central opening and attached to the driven member,

said connecting member having an enlarged head at its upper end forming an annular projecting .flange seating on said annular shoulder, and frangible cylindrical pins extending down through the upper face of the flange, connecting the housing and the connecting member, imparting the rotary movement to the driven member and operating to shear and permit free rota tion of the housing when a predetermined torque is being imparted through the same.

3. In safety drilling apparatus to be connected into a drill string in drilling a deep well with a rotary table, the combination of a tubular driving housing having a head at its lower end with a central opening through the same with an annular supporting shoulder formed on the upper face of the head, a driven member below the housing, a tubular connecting member extendingdown through the said central opening and attached to the driven member, said connecting member having an enlarged head at its upper end forming an enlarged projecting flange seating on said annular shoulder to support the drill string, saii flange having a plurality of holes extending down through the same, said shoulder having a plurality of sockets aligning with said determined torque is being same.

l. In safety drilling apparatus to be connected into a drill string in drilling a deep well with a rotary table the combination of a tubular driving housing having a head at its lower end with a central opening through the same with an annular supportingshoulder formed on the up per face of the head, a'driven member helowthe housing, a tubular connecting member extend ing down through the said central opening and attached to the driven member, said connecting member having an enlarged head at its upper end forming an enlarged projecting flange seat= ing on said annular shoulder to support the drill. string, said flange having a plurality of holes extending down through its upper face, and said shoulder having a plurality of sockets aligning with the holes, and frangible cylindrical pins mounted from above in the said holes and sock" ets for imparting the rotary movement to the driven member and operating to shear and permit free rotation of the housing when a predetermined torque is being imparted through the impartedthrough the 5. In a safety drilling apparatus for deep wells, I

the combination of an upper rotary driving memher having an annular supporting shoulder, a lower driven member to be connected to the drill string, and having a central threaded socket, a connecting member attached to the driven memher in the threaded socket, and having an annular flange projecting laterally from the same and supported on the said annular shoulder, and frangible cylindrical pins extending down through the upper face of the flange imparting the driving movement from the upper member to the driven member, said pins operating to brealr and permit movement of the driving member independently of the driven member when a predetermined torque is being imparted through the same.

ZARA WZTKIN. 

